This error can occur when the folder that contains Adobe Acrobat or Adobe Reader, or one of it parent or sub-directories has been renamed or moved, or Adobe Reader or Acrobat has otherwise become confused which exact application to use as helper application within the browser.
SOLUTION
Solution 1: Make sure the registry setting that tells the browser where to find Adobe Acrobat or Adobe Reader is correct.
Disclaimer: The registry contains system-related information that is critical to your computer and applications. Before modifying the registry, be sure to make a backup copy of it. Adobe doesn't provide support for problems that may arise from improperly modifying the registry. Adobe strongly recommends that you have experience editing system files before you modify the registry. For information on the Windows Registry Editor, see the documentation for Windows or contact Microsoft Technical Support.
Go to Start > Run
Type regedit and click OK.
Browse to the following key: HKEY_CLASSES_ROOT\Software\Adobe\Acrobat\Exe
Make sure that the correct Default data value is set for the path where Adobe Reader or Acrobat are installed.
The default installation values are "C:\Program Files\Adobe\Reader 9.0\Reader\AcroRd32.exe" or "C:\Program Files\Adobe\Reader 9.0\Reader\Acrobat.exe", depending on whether Adobe Reader or Adobe Acrobat is installed.
Solution 2: Configure the browser to use Acrobat or Adobe Reader as a helper application.
After you configure Acrobat or Adobe Reader as a helper application, the browser starts the helper application in a separate window and displays PDF files within that window. Acrobat and Adobe Reader both include a preference that lets you specify Acrobat or Adobe Reader as the helper application.
To configure Acrobat or Adobe Reader as a helper application:
Start Acrobat or Adobe Reader.
Choose Edit > Preferences.
Select Internet on the left.
Deselect Display PDF In Browser Using [Acrobat application], and then click OK.
Quit Acrobat or Adobe Reader.
The next time you select a link to a PDF file in the browser, a dialog box asks what you would like to do with the file. If you select Open It, the browser opens the PDF file in Acrobat or Adobe Reader (the helper application); if you select Save It To Disk, the browser saves the PDF file to your hard drive.
Solution 3: Make sure all previous version of Acrobat and Adobe reader are removed from your computer.
Make sure all previous versions of Acrobat and Reader have been removed from your computer. Reinstall from Acrobat disk or download. In the case of Reader install from the download. If installing on Vista then right-click on the Installer and choose to Run As Administrator.
Solution 4: Run Acrobat/Reader in a new local administrator account.
Create a new user account that has the same permissions as the account you use when the problem occurs, or create a new local administrator account. If the problem doesn't recur when you are logged on to the new account, then the original user account may be damaged.
